The place I work we have a issue with other employees going into drawings and changing them.  Is there any way to make the cad drawings read only?  Or is there a way to monitor who is making the changes and when?

To monitor and log file operations you'd need a document management system - e.g. Autodesk Vault.
You can place drawings in a network folder with restricted access (R/O flag) or you can use something like CADVault (DWG drawing protection, DRM).